Heretofore, there have been known internal grinders for cutting or grinding an inner surface of a cylinder or a ring gauge. As shown in FIG. 1, the conventional internal grinder has been normally constructed such that a ring-shaped work 1 is clamped by a chuck 2 and rotated, an inner surface of the work 1 is ground by a grind stone 4 affixed to a spindle 3 movable in a diametral direction of this work 1 or along the inner surface thereof.
However, in the case of the conventional internal grinder with the above-described arrangement, grinding of the work 1 is concentrated at one portion, to which is abutted the grind stone 4, and hence, such disadvantages have been presented that it is difficult to achieve uniformalization of grinding and the work 1 tends to become elliptical.
Furthermore, in the conventional internal grinder, a spindle 3 of the grind stone 4 is moved in the diametral direction of the work 1 and along the inner surface of the work 1, whereby vibrations tend to be caused to the spindle 3, thus affecting the accuracy of grinding.
Further, as for the chuck 2, there have been many cases of adopting three-point chucks as shown in FIG. 1, whereby the work 1 cannot be clamped by the chuck 2 unless it is round-shaped, and troublesome centering work is required for the chuck 2 to clamp the work 1.
Moreover, the grind stone 4 has had to be often replaced with new one depending on the wear of the grind stone. In this case, rotation of the grind stone must be stopped each time replacement is effected, thus resulting in lowered workability.
The present invention has as its object the provision of an internal grinder, in which the center alignment of the work is simplified, grinding accuracy is improved, and the workability is excellent.